The number of people who play golf is continuously on the increase. However, the reality is that those who want to play golf cannot always go out on a golf course, so a virtual golf system (or a screen golf system) allowing people to virtually play gold at low costs even in downtown areas or the like is widely spreading. This virtual golf system is basically based on a concept that when a golfer hits a golf ball toward a screen, the virtual golf system detects a movement of the golf ball and virtually displays on a screen the results of hitting the golf ball obtained through a certain simulation process. In this virtual golf system, it is important that the height of the golf ball, a movement speed, a movement direction, and the like is measured to make a simulation to allow the golfer to feel the movement of the golf ball as he/she is actually playing on a golf course.
To this end, in most of the conventional virtual golf systems, information regarding a movement of the hit golf hole is collected and calculated by using a high-priced optical device such as a high speed camera or the like, but this method requires a considerably complicated technique and, most of all, it incurs a great amount of cost in implementing the virtual golf system.
Also, Japanese Patent Laid-Open Publication No. 2003-230767, U.S. Pat. No. 5,390,927, Japanese Patent No. 3394978, and the like disclose prior arts of detecting a movement of a golf ball by using a plurality of horizontal sensors and a plurality of vertical sensors, but the use of such prior arts still has a problem in terms of the complexity, implementation costs, or the like of the virtual golf system.